A suspected gunman who dressed as a policeman killed at least 16 people, including a police officer, in Nova Scotia, Canadian police say.
The 12-hour rampage ended in a car chase and the attacker is also dead.
Residents in the rural town of Portapique had been advised to lock themselves indoors after the attack began on Saturday.
The gunman shot people in several locations across Nova Scotia which meant authorities were still trying to establish the final death toll, police said on Sunday.
The police warned that there may be more victims.
Police earlier said the suspect drove what appeared to be a police car.
Royal Canadian Mounted Police Constable (RCMP) Heidi Stevenson, who had served in the force for 23 years, was among those killed.
Heidi answered the call of duty and lost her life while protecting those she served," Nova Scotia RCMP Commanding Officer, Assistant Commissioner Lee Bergerman said in a Facebook post.
"Two children have lost their mother and a husband his wife. Parents lost their daughter and countless others lost an incredible friend and colleague," Mr Bergerman said.
RCMP Commissioner Brenda Lucki said she believed the gunman had an initial "motivation" at the beginning that "turned to randomness", according to CBC News
Canadian Prime Minister Justin Trudeau described it as "a terrible situation" and Nova Scotia Premier Stephen McNeil told reporters "this is one of the most senseless acts of violence in our province's history."
Police say they were first alerted to an incident involving firearms late on Saturday.
Tweets by Nova Scotia police identified the alleged attacker as 51-year-old Gabriel Wortman.
He was not employed by the Royal Canadian Mounted Police but "may be wearing a RCMP uniform", they said.
"There's one difference between his car and our Royal Canadian Mounted Police vehicles: the car # [registration plate]. The suspect's car is 28B11, behind rear passenger window. If you see 28B11 call 911 immediately," they tweeted on Sunday.
#Colchester: Gabriel Wortman may be driving what appears to be an RCMP vehicle & may be wearing an RCMP uniform. There's 1 difference btwn his car and our RCMP vehicles: the car #. The suspect's car is 28B11, behind rear passenger window. If you see 28B11 call 911 immediately. pic.twitter.com/yyeOeBt8Ui— RCMP, Nova Scotia (@RCMPNS) April 19, 2020
The gunman later changed cars to drive a "small silver Chevrolet SUV", police added.
Mass shootings are relatively rare in Canada where gun ownership laws are stricter than in the neighbouring United States.
In 2019 two fugitive teenagers confessed to killing three people, including an Australian-US couple on holiday, in northern British Columbia.
In 1989 a college shooting in Quebec left 14 women dead after the killer sent all the men out of the classroom and opened fire.